Electric switch



Dec. 4, 1945. T. E. GRAVES 2,390,145

ELECTRIC SWITCH Filed Aug. 20, 1945 INVENTOR. 7fieodore E Graves Patented Dec. 4, 1945 ELECTRIC SWITCH ,4 Theodore Eliot Graves, Orange, N. J., asslgnor to The Wilcolator Company, Elizabeth, N. 1., a

corporation of Delaware Application August 20, 1943, Serial No. 499,367 6 claims. (01. 200-140) This invention relates to thermostatic switches and is directed to the provision of a thermal limit switch provided with means for resetting it manually.

A switch constructed in accordance with the invention is provided with an expansible and contractible element which is connected to the movable switch-member so as to operate that member with a snap action in one direction to open or close the contacts controlling the circult. The connection from the expansible and contractible element to the switch member is subject to adjustment whereby the actuation of the switch-member will occur at any selected temperature. Associated with these parts is a manual resetting device by which the switchmember may be moved in a direction opposite to that in which it is moved by the expansible and contractible element.

In accordance with the invention a spring is provided for yieldingly opposing movement of the expansible and contractible element in a direction to actuate the switch-member and the force exerted by this spring is such that while it is suflicient to load the expansible and contractible element adequately to insure the desired operation, it is not suiiicient to effect movement of the switch-member in the direction opposite to that in which it was moved by the element. Thus, when the expansible and eontractible element moves the switch-member in one direction against the tension of the spring to open or close the circuit when the selected temperature is reached, the switch-member will remain in the position to which it is moved until the manual resetting device is actuated to efiect the reverse movement of the switch-member.

The preferred embodiment of the invention is illustrated in the accompanying drawing in which Fig. 1 is a sectional elevation of a switch structure, and Fig. 2 is a similar view on a smaller scale showing various of the operating parts in positions other than those in which they appear in Fig. 1.

Many of the elements of the new switch mechanism are similar to those illustrated and described in U. S. Letters Patent No. 2,197,229, granted April 16, 1940.

The parts of the switch mechanism are mounted upon, and many of them are enclosed within, a casing consisting of a box member 3 and a cover member 4 secured together by screws 5 as indicated. Within this casing is a switch member 6 which is pivoted at one end and is adapted to be rocked about this pivot in the operation of the switch. The pivotal mounting of the member 6 is preferably a knife-edge mounting, the member 6 being supported by a screw stud l which has a V-shaped groove in its head receiving the knife-edge formed upon the switch lever 6.

The switch lever 6 is moved in one direction to open or close circuit-controlling contacts by an expansible and contractible element in the form of a bellows 8 mounted in a cup 9 which is secured upon the back plate l by screws Hi. The cup has a capillary tube ll secured-"to it in communication with the interior of the cup and this tube ll leads to a bulb located within the chamber whose temperature is to control the operation of the switch. The open end of the bellows is secured to an annulus I! mounted within the cup 9.

Extending within the bellows 8 is a plug or stud l3 having an enlarged head M at one end and at the other end an opening whose wall is threaded to receive the threaded end l5 of a rod I6. Surrounding the plug I3 is a spring ll bearing at one end upon the head H of the plug and at the other against an annulus l8 which is held in position between the flange of cup 9 and the back plate 4 of the casing by the screws Hi. The rod 16 is provided with a flange l9 interme-- diate its ends and its end opposite the screw I5 is provided with projections 28 extending into axial. grooves M in the end of a rod 22 which is mounted for rotation in a suitable bore in the casing 3. This rod 22 carries a handle 23. The handle may be rotated nearly a full revolution, its rotational movement being limited by a stud 24, and it is held in the position to which itis moved by a friction spring 25.

The pivoted switch arm 5 has an opening through which the rod l6 extends and the metal on either side of this opening is bent as shown to form rockers which bear upon the surface of the flange I9. At its opposite end the arm 6 is connected to an actuating spring formed of a piece of sheet metal cut to provide three arms, the central one of which is bowed as shown. The two outer arms 26 of this spring are secured at their lower ends to the cover 4 of the casing by screw studs 21. At their upper ends these arms 26 of the spring are integral with each other and with the central arm 28 whose lower end is provided with knife edges received in a circumferential V-shaped groove in a stud 29 mounted upon the lower end of the switch arm 6. At their upper ends where the three arms of the spring are joined they carry a piece 30 to which a contactof a cotter-pin 32.

corresponding reverse move flange I! to the right.

carrying block 3i is secured loosely as by means This block 3| carries contacts 33 which coact with contacts 34 mounted upon the casing 3.

The central arm 28 of the three-part spring is bowed as shown between its knife-edge contact with thestud 29 on the switch arm and its point oi connection to the other two arms 26 of the spring, and by reason of this bowed condition it subjects the switch arm 6 to pressure tending to turn it about its pivot in a counterclockwise direction. -The spring l'l acting upon the plug I 3 tends to move the plug to the left and in such movement the flange ii! on rod I6 engages the switch arm 6 to move it in a clockwise direction. This spring I! is so formed that while it exerts a pressure on plug I3 suificient to hold flange l9 against the rockers formed on switch arm 6, it is not of suflicient strength to actuate the parts l3 and 16 to rock the switch lever from the position in which it is shown in Fig. 1 to that in which it is shown in Fig. 2. Because of this, the switch arm 6 and the contacts controlled thereby are moved in one direction by spring 28 when permitted by the contraction of the bellows resulting in movement of the parts l3, I, I and IE to the right and consequent movement of the switch arm 6; but when the bellows 8 expands the sprin I! does not effect ent. To'efiect such reverse movement the switch arm '6 has a manualre-setting rod 35 connected to it. This rod is mounted for axial movement in a bore in the casing 3; it is provided with a head 36 at one end and at its opposite end it is loosely secured by rivet 31 to the switch arm 6.

The switch may be set for operation at any selected temperature by depressing head 36 to close the contacts; and turning the handle 23 by reference to scale markings on it cooperating with a fixed index as is usual. In this rotational movement the rod 22 of the handle operates to turn the rod l6, and the threads upon the parts I! and i5 operate to vary the position of the flange [9 with reference to the head H of the part l3. When the selected temperature is reached the liquid in the bulb and the tube ll connected to bellows 8 causes the bellows to contract'and thereby move the part l3 and flange l'9 to the right. The bowed spring 28 applies pressure to the switch arm 6 and causes it to turn about its pivot to follow the movement of the When the lower end of spring 28 passes across the center of the threepart spring it moves the upper end of the spring to the left with a snap action, thereby actuating the contact-carrying block 3| to carry the contacts 33 out of engagement with the stationary contacts 34 and thereby open the controlled circuit, or, if desired, the movement may be arranged to close the circuit.

If the temperature applied to the bulb were to fall to such extent as to permit expansion of the bellows 8, the rod l6 and its associated parts would not be moved to the left by spring I1 with resultant movement of the switch arm 6 and the spring 26-48 to close the circuit-controlling contacts. Instead, the contacts would remain in the position to which they were moved, the open position in this instance. Closing of the circuit is effected manually by depression of the handle 36 on rod 35. This turns the switch arm 6 about its pivot in a clockwise direction and carries the lower end of the bowed spring arm 28 across center, thereby actuating the three-part spring to contacts 34.

move the contact-carrying block 3| back to its initial position with the contacts 83 engaging the This manual operation resets the switch in its original condition in readiness for a further operation in response to the selected temperature condition. During this manual operation the flange IS on the rod l8 follows in engagement with the switch arm 6 under the action of the spring H, the tension of which holds the switch arm 8 in its reset position for later operation in response to the contraction of the bellows 8.

If, on the other handyit is desired to again open the circuit before the thermal element has reached the temperature at which it would open the circuit, the handle, 36, may be pulled out thereby carrying the bowed spring arm, 28, across center and opening the contacts with a snap; thus, the manual reset means may be used c mally biasing the member toward one of its positions, manual means for causing movement of the member to the opposite position accompanied by actuation of the snap-acting spring, and

spring means separate from said snap-acting spring acting to hold the member in the lastmentioned position, said spring means being effective to hold the member in that position when it has been moved there by the manual means but not to move it to that position against the tension of the snap-acting spring.

2. A thermostatic switch comprising the combination of a pivoted switch member, a contact positioned thereby, a thermo-responsive element controlling movement of the switch member in one direction in response to a change of temperature, a spring opposing such movement of the switch member in response to the thermo-responsive element, a snap-acting mechanism separate from said spring for moving the switch member in response to action of the thermo-responsive element on a predetermined change of temperature, and a handle connected to the switch member for moving it in a direction opposite to that in which it is moved by the snap-acting mechanism, the said spring being of insufllcient power to efiect the movement oi! the switch member which is effected by the handle against the tension of the snap-acting mechanism.

3. A thermostatic switch omprising the combination of a pivoted switch member, contacts controlled by the movement thereof for opening and closing a circuit, a spring formed 0! sheet metal and consisting of two or more parts integrally connected and having at least one of the parts bowed to apply pressure to the switch member tending to turn it'in only one direction,

- thermo-responsive element connected to the switch member and controlling movement there ofoccasioned by said spring, and a second spring opposing movement of the thermo-responsive element in a direction for eflecting movement of the switch member by the first spring but 0! insuflicient power to effect reverse movement thereof, such reverse movement being eflected only by said handle.

4. In a thermostatic switch having a snapacting mechanism including a member movable to either of two positions and an electrical contact positioned thereby, a snap-acting spring normally biasing the member toward one only of said positions, said electrical contact being mounted on said spring, manual means for causing movement of the member to the opposite position accompanied by simultaneous reverse actuation of the snap-acting spring, and a second spring separate from said snap-acting spring acting to hold the said member in the said lastmentioned position against the biasing tension of said snap-acting spring.

5. In a thermostatic switch having a snapacting mechanism including a snap-acting spring and a member movable to either of two positions, an electrical contact positioned by said mechanism, said snap-acting spring normally biasing the member toward one only of said positions, manual means for causing movement of the member to the opposite position, and a second spring separate from said snap-acting spring acting to hold the said member in the said lastmentioned osition against the biasing tension of said snap-acting spring, and temperature-responsive means for acting on said member against the holding action of said second spring at a predetermined temperature whereby said member is movable by said snap-acting spring at said temperature.

6. A thermostatic switch comprising the combination of a pivoted switch member, contacts controlled by the movement thereof for opening and closing a circuit, a spring formed of sheet metal consisting of a plurality of parts integrally connected and having at least one of the parts bowed to apply pressure to the switch member tending to turn it in only one direction, said contacts being carried solely by a part of said spring, a handle connected to the switch member for turning it manually in a direction opposite to that caused by said spring, a thermo-responsive element for controlling the action or said spring in effecting the movement of said switch member, said element comprising an expansible and contractible bellows connected to the pivoted switch member, adjustable mechanism for selecting a temperature and for simultaneously adjusting the connection from the bellows to the switch member, and a second spring acting upon the switch member inopposition to the movement thereof by the first spring, said second spring being of insufilcient power to efiect a movement of the switch member against the tension of the first spring but being adapted and arranged to hold said switch member in the position set by said handle against the turning action of said first spring.

THEODORE ELIOT GRAVES. 

